Culture of lactic acid bacteria is carried out in various manners; most widely by using animal milk in the production of lactic acid bacteria preparations, and also in production of fermented milk, lactic acid bacteria beverages, cheese, etc. However, generally, lactic acid bacteria have different auxotrophy depending on the species, and in general do not sufficiently grow in a medium consisting of only animal milk. Therefore, even with a strain having relatively good proliferability among lactic acid bacteria, culture should be continued for as many as several days to obtain a fermentation product such as fermented milk or lactic acid bacteria beverage, of sufficient acidity upon its production.
Such long-time culture of lactic acid bacteria, however, causes reduction in the viable cell count, and therefore, is not necessarily considered to be a preferred culturing method for the production of lactic acid bacteria beverages, fermented milk, or the like all of which place importance on the viable cell count in expectation of various physiological effects.
In producing various beverages or foods each of which places importance on the flavor of a lactic acid bacteria fermentation product, on the other hand, strains to be used cannot be selected solely from the viewpoint of their proliferativeness. Lactic acid bacteria of poor proliferativeness may be used in some instance for the availability of fermentation products with good flavor.
In the culture of lactic acid bacteria, it is, therefore, common practice to add various growth-promoting substances beforehand to a medium for the purpose of improving the efficiency of the culture. Examples of growth-promoting substance, which are generally considered to be effective, include chlorella extract, iron salts, vitamins, proteolytes including amino acids or peptides, and yeast extract.
Further, as other techniques intended to promote the growth of lactic acid bacteria, there have been recently, reported a method making use of an aqueous extract of sake lees and/or an aqueous extract of sake lees which has been treated with a protease (Patent Document 1), a method making use of an extract from leaves of a plant of Coffea arabica (Patent Document 2), a method making use of papaya flesh parts including their skins (Patent Document 3), a method making use of an extract from algal bodies of marine microalgae (Patent Document 4), a method making use of one or more vegetables or the like selected from the group consisting of brocolli, cauliflower, kale, sheperd's purse, radish, tower mustard, celery-leaved buttercup, white celery mustards Japanese bittercress, yellow rocket, watercress, leaf mustard, brown mustard, wasabi (green horseradish paste), herbaceous perennial, long Japanese turnip, Japanese pickling turnip, turnip, oilseed rape, cabbage, spinach, komatuna (Brassica campestris var. peruviridis), celery, parsley, lettuce and apple (Patent Document 5), a method making use of one or more kinds of vegetables or the like selected from the group consisting of dishcloth gourd, cucumber, sweet melon, pumpkin, yam, taro, ‘KONJAK’, Japanese radish, carrot, tomato, green pepper, okra, Welsh onion, Chinese cabbage, bean sprouts and tangerine orange (Patent Document 6), a method making use of a tea extract (Patent Documents 7 and 8), a method making use of a calcium salt (Patent Document 9) and a method making use of an extract of ginger, tea or green onion (Patent Document 10), etc.
In order to maintain the usefulness or the efficacy of lactic acid bacteria, however, it is necessary not only to promote the growth of the bacteria but also to reduce death of the bacteria and to improve the viability of the bacteria in the fermentation product by the lactic acid bacteria. Generally, a reduction in the viability of lactic acid bacteria becomes pronounced when preparing a low-fat fermented milk food containing lactic acid bacteria fermentation product of skim milk powder or the like, or when lactic acid fermentation has proceeded too much. The reduction in the viability of lactic acid bacteria, therefore, becomes more serious when preparing a low-calorie fermented milk food or a low-pH fermented milk food. Chlorella or the like is known as a material usable to prevent a viability reduction of lactic acid bacteria, and to maintain the cell count of lactic acid bacteria in a fermented milk food.
In the production of a beverage or food such as a lactic acid bacteria fermentation product or a fermented milk food containing the same, however, a conventionally-known substance added for promoting the growth of lactic acid bacteria or a conventionally-known substance added for improving the viability of lactic acid bacteria may affect the flavor itself of the product in many instances and may also cause a rise in product cost, when used in such an amount as bringing about sufficient effects. Furthermore, even if it is possible to maintain a state that a large amount of viable lactic acid bacteria are contained, the lactic acid bacteria can not be maintained active, thereby making it difficult to expect sufficient physiological effects in some instances.                [Patent Document 1] JP-A-05-015366        [Patent Document 2] JP-A-06-125771        [Patent Document 3] JP-A-07-023777        [Patent Document 4] JP-A-07-051057        [Patent Document 5] JP-A-11-266860        [Patent Document 6] JP-A-02-242667        [Patent Document 7] JP-B-2667421        [Patent Document 8] JP-B-3223326        [Patent Document 9] JP-B-2673333        [Patent Document 10] JP-A-2001-190272        